Redox curved screens are robustly built and require a minimum of maintenance and attention, as the raw waste water is pumped over a curved, wedge wire, screen plate where separated particles slide down, and the screened water leaves the screen via the outlet. The screen can be equipped with a programmable spray cleaning device in case the waste water contains fiber-like materials or fat, and for heavy polluted waste water, a vibrating screen plate can be installed to guarantee clog-free operation.